The enormous advances in microelectronics now enable extensive analog and digital signal processing, even in a restricted space. The availability of analog and digital signal processors with minimum spatial dimensions has also paved the way in recent years for their use in hearing aids, clearly an application in which system size is essentially limited.
In the case of hearing aids, a simple amplification of an input signal from a microphone often leads to unsatisfactory results because interference signals are also amplified at the same time and this limits the benefit for the user to special acoustic situations. For several years, digital signal processors that digitally process the signal from one or more microphones have therefore been fitted in hearing aids, so that, for example, selected unwanted noise can be appropriately suppressed.
Modern signal processing methods mainly include a “Blind Source Separation” (BSS), with an input signal from several acoustic sources being broken down into discrete signals. Furthermore, a classification of the input signal is known whereby the actual acoustic situation is classified according to classification variables, such as the input signal level. For example, an input signal can then be broken down into two discrete signals and differentiated by a classification, with the discrete signals being fed, amplified if required, to the user. Furthermore, parameters in the hearing aid, can, for example, be changed so that a directional microphone is activated in order to suppress sound sources from the rear semi-plane.